Golf club shaft and golf club

ABSTRACT

Provided are the golf club shaft and the golf club for offering excellent feel of swing motions without demanding fine setting while keeping advantages of the short-sized golf club shaft. The golf club shaft includes a shaft body which extends in a longitudinal direction, and a gravity center shifting member attached to the shaft body for shifting a shaft gravity center toward a distal-end side in the longitudinal direction. In the case where the shaft body is cut to have a shaft full length of 43 inches or shorter, and positions of a distal-end portion and a proximal-end portion in the longitudinal direction are defined by percentage as 0% and 100%, respectively, a position of the shaft gravity center is set to be in a range from 39% to 45%.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a National Stage application of International Patent Application No. PCT/JP2018/046287 filed on Dec. 17, 2018, which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a golf club shaft and a golf club.

BACKGROUND OF THE INVENTION

The patent right has been granted to the applicant of the present invention which relates to a golf club shaft (Japanese Patent No. 4880063). Specifically, the golf club shaft includes a metal cylinder entirely made of metal material, and a hollow cylindrical shaft body which includes at least a part of the metal cylinder in the longitudinal direction, and is produced through thermosetting treatment of multiple unset thermosetting resin prepregs which have been laminated and wound on the outer circumference of the metal cylinder. The metal cylinder is located at a part of the hollow cylindrical shaft body in the longitudinal direction. At least an outer radial part of the metal cylinder is buried in the burying recess cylindrical portion formed in the inner wall of the shaft body to bring the hand-side cylindrical end surface of the metal cylinder into abutment on the hand-side recess cylindrical end surface of the burying recess cylindrical portion of the shaft body.

SUMMARY OF THE INVENTION

The applicant, for example, has been proceeding with research and development of the so-called short-sized golf club shaft formed by cutting the shaft body with full length longer than 43 inches (for example, 45 inches or longer) to have its full length of 43 inches or shorter. The short-sized golf club shaft can be easily handled to accurately meet an impact at the sweet spot, resulting in the improved meeting rate.

Meanwhile, the use of the short-sized golf club shaft is likely to make especially the advanced golf player feel like unnatural sense of swing motions, resulting in disadvantages that the ball hitting angle tends to be small (difficulty in rise-up of the ball). Increase in the club head weight to be heavier than the club head to be attached to the normal-sized golf club shaft has been taken into account for the purpose of using the short-sized golf club shaft.

As increase in the club head weight affects the weight and balance of the entire golf club, fine setting including adjustment of the full length of the short-sized golf club shaft may be demanded depending on the circumstances.

The present invention has been made in view of the above-described problem, and it is an object of the present invention to provide the golf club shaft and the golf club, which are effective for offering excellent feel of swing motions without demanding the fine setting while keeping advantages of the short-sized golf club shaft.

The golf club shaft of the embodiment includes a shaft body which extends in a longitudinal direction, and a gravity center shifting member which is attached to the shaft body for shifting a shaft gravity center toward a distal-end side in the longitudinal direction. In the case where the shaft body is cut to have a shaft full length of 43 inches or shorter, and positions of a distal-end portion and a proximal-end portion in the longitudinal direction are defined by percentage as 0% and 100%, respectively, a position of the shaft gravity center is set to be in a range from 39% to 45%.

Assuming that each position of the distal-end portion and the proximal-end portion in the longitudinal direction is defined by percentage as 0% and 100%, respectively, it is preferable to set the position of the shaft gravity center to be in the range from 41% to 44%, and more preferably, from 42.5% to 43.5%.

A cut length of the shaft body at the proximal-end side in the longitudinal direction may be made longer than a cut length of the shaft body at the distal-end side in the longitudinal direction. The concept of the cut length applies to the case in which the cut length at the distal-end side is zero. That is, there may be the case of cutting the shaft body only at the proximal-end side without cutting at the distal-end side besides the case of cutting the shaft body both at the distal-end side and the proximal-end side.

The weight ratio of the gravity center shifting member to the shaft body may be set to be in a range from 14% to 33%.

Preferably, the weight ratio of the gravity center shifting member to the shaft body is set to be in the range from 17% to 30%, and more preferably, from 20% to 25%.

The gravity center shifting member may be provided with a metal cylinder buried in an inner circumferential surface of the shaft body.

The shaft body may be configured to include a first region having a shaft outer diameter relatively gently reduced, a second region having the shaft outer diameter relatively steeply reduced, and a third region having the smallest relative change amount of the shaft outer diameter, which are sequentially arranged from the proximal-end side toward the distal-end side in the longitudinal direction.

It is possible to set an occupancy percentage of the first region in the longitudinal direction to 30% or higher, an occupancy percentage of the second region in the longitudinal direction to be in a range from 45% to 60%, and an occupancy percentage of the third region in the longitudinal direction to be in a range from 10% to 25%.

It is possible to attach a grip to an outer circumferential surface of the first region, and bury a metal cylinder as the gravity center shifting member in an inner circumferential surface of the third region.

The golf club according to the embodiment may be configured to have a club head and a grip attached to any one of the golf club shafts as described above.

The present invention ensures to provide the golf club shaft and the golf club for offering excellent feel of swing motions without demanding the fine setting while keeping advantages of the short-sized golf club shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of an external appearance of a golf club structure according to an embodiment.

FIG. 2 illustrates an example of a schematic structure of a golf club shaft according to the embodiment.

FIG. 3 illustrates in an enlarged view an abutted part between a shaft body and a metal cylinder, which is encircled in FIG. 2.

FIG. 4 is a view of the golf club shaft illustrated by FIG. 2 when seen from a distal-end side.

FIG. 5 represents properties of three samples of the golf club shaft according to the embodiment.

FIG. 6 represents an example of change in a shaft outer diameter of the golf club shaft in the longitudinal direction according to the embodiment.

FIG. 7 represents an example of each change in the shaft outer diameter of the golf club shafts in the longitudinal direction according to the embodiment and modified examples 1 to 3.

FIG. 8 represents an example of a laminated prepreg structure constituting the shaft body.

DETAILED DESCRIPTION

FIG. 1 illustrates an example of an external appearance of a structure of a golf club 10 according to an embodiment. The golf club 10 includes a longitudinally extending golf club shaft 100, a club head 200 attached to a distal-end side (tip side) of the golf club shaft 100, and a grip 300 attached to a proximal-end side (butt side) of the golf club shaft 100. FIG. 1 illustrates the club head 200 formed as an iron club head. However, the club head 200 may be formed as a driver club head.

Referring to FIGS. 2 to 4, the schematic structure of the golf club shaft 100 of the embodiment will be described. FIG. 2 illustrates the golf club shaft 100 having the shaft outer diameter tapered from the proximal-end side (butt side) to the distal-end side (tip side) at a constant taper ratio for convenience of making the drawings. Actually, the shaft outer diameter of the golf club shaft 100 is configured characteristically as described later referring to FIG. 6.

The golf club shaft 100 includes a hollow cylindrical shaft body 110 made of fiber reinforced resin, and a metal cylinder (gravity center shifting member, weight) 120 attached to the distal-end side of the shaft body 110.

The shaft body 110, for example, is made of FRP (Fiber Reinforced Plastics) produced through thermosetting treatment of multiple unset thermosetting resin prepregs, which have been laminated and wound. The shaft body 110 (golf club shaft 100), so-called short-sized shaft body (golf club shaft) is produced by cutting the longitudinally extending shaft body 110 with its full length of 43 inches or longer (for example, 45 inches or longer) in the initial state to have the full length of 43 inches or shorter in use. The cut length of the shaft body 110 at the proximal-end side in the longitudinal direction is longer than the cut length of the shaft body 110 at the distal-end side in the longitudinal direction. The concept of the cut length applies to the case in which the cut length of the shaft body 110 at the distal-end side is zero. It is possible to cut the shaft body 110 only at the proximal-end side without being cut at the distal-end side besides the case of cutting both at the distal-end side and the proximal-end side. The confirmation whether the shaft body 110 has been cut for adjusting (reducing) the shaft full length may be made by observing at least one of the distal-end surface and the proximal-end surface of the shaft body 110.

The metal cylinder 120 is attached to the distal-end side of the shaft body 110 for shifting the shaft gravity center (gravity center position of the golf club shaft 100, balance point) toward the distal-end side. The metal cylinder 120 is made of metal material, for example, stainless steel, iron, aluminum, tungsten, and the like. However, the metal cylinder may be made of any other materials without restriction so long as the weight of the metal cylinder is increased. Instead of using the metal cylinder 120, it is possible to use the resin cylinder made of resin material, for example, thermoplastic resin, thermosetting resin, rubber and the like as the “gravity center shifting member, weight”. Examples of the thermoplastic resin include polypropylene, polyterephthalate, polyethylene and the like. Examples of the thermosetting resin include epoxy resin, phenol resin, unsaturated polyester resin, polyurethane, polyimide, and the like. Examples of the rubber include chloroprene rubber, fluororubber, chlorinated polyethylene, nitrile rubber, isobutylene-isoprene rubber, ethylene-propylene rubber, and the like.

As FIG. 3 illustrates, a burying recess cylindrical portion 112 is formed in an inner wall 111 of the shaft body 110 at an end portion of the distal-end side. The metal cylinder 120 has its outer radial portion buried in the burying recess cylindrical portion 112 (the metal cylinder 120 is buried in the inner circumferential surface of the shaft body 110). A proximal-end side cylindrical end surface 121 of the metal cylinder 120 is brought into abutment on a proximal-end side cylindrical end surface 113 of the burying recess cylindrical portion 112 in the longitudinal direction. The structure ensures to improve durability of the golf club shaft 100 by preventing the metal cylinder 120 from falling out from the shaft body 110 toward the proximal-end side even if the impact is exerted upon swing or strike motions. The club head 200 attached to the end portion of the distal-end side of the shaft body 110 prevents the metal cylinder 120 from falling out from the shaft body 110 toward the distal-end side even if the impact is exerted upon swing or strike motions.

Preferably, an abutment length A of an abutted area between the proximal-end side cylindrical end surface 121 of the metal cylinder 120 and the proximal-end side cylindrical end surface 113 of the burying recess cylindrical portion 112 is set to be in the range from 0.05 mm to 0.5 mm. If the abutment length A is shorter than 0.05 mm, there may be the case in which the metal cylinder 120 falls out from the shaft body 110 toward the proximal-end side when the impact is exerted upon swing or strike motions. If the abutment length A is longer than 0.5 mm, the shaft body 110 becomes so thin that there may be the risk of dent, cut, and breakage of the fiber reinforced resin layer of the shaft body 110 at the abutted area between the proximal-end side cylindrical end surface 121 of the metal cylinder 120 and the proximal-end side cylindrical end surface 113 of the burying recess cylindrical portion 112.

As FIGS. 3 and 4 illustrate, a distal-end side cylindrical end surface 122 of the metal cylinder 120 is exposed from a shaft distal-end side end surface 114 of the shaft body 110. It is possible to confirm whether the metal cylinder 120 is buried at the shaft distal-end side by visually observing the shaft distal-end side end surface 114 of the shaft body 110. This allows the metal cylinder 120 to perform the function of shifting the gravity center of the golf club shaft 100 toward the shaft distal-end side.

It is assumed that the golf club shaft 100 of the embodiment has the shaft body 110 which has been cut to have its full length of 43 inches or shorter, and positions of the distal-end portion and the proximal-end portion of the shaft body 110 are defined by percentage as 0% and 100% in the longitudinal direction, respectively. The shaft gravity center which has been shifted by the metal cylinder 120 is positioned in the range from 39% to 45%. Assuming that the positions of the distal-end portion and the proximal-end portion are defined by percentage as 0% and 100% in the longitudinal direction, respectively, preferably, the shaft gravity center which has been shifted by the metal cylinder 120 is positioned in the range from 41% to 44%, and more preferably, from 42.5% to 43.5%.

By setting the position of the shaft gravity center which has been shifted by the metal cylinder 120 to be in the above-described range, various parameters of the golf club shaft 100 such as weight, frequency, and torque may be easily adjusted. The structure allows excellent feel of swing motions without requiring fine setting while keeping advantages of the short-sized golf club shaft 100.

When the shaft gravity center shifted by the metal cylinder 120 is positioned closer to the distal-end side than the position corresponding to 39% (below the lower limit of condition formula), it is difficult to adjust the various parameters of the golf club shaft 100 such as weight, frequency, and torque.

When the shaft gravity center shifted by the metal cylinder 120 is positioned closer to the proximal-end side than the position corresponding to 45% (in excess of the upper limit of condition formula), it is difficult to eliminate disadvantages as a result of using the short-sized golf club shaft 100 (unnatural sense of swing motions, difficulty in rise-up of the ball). Increase in the weight of the club head for eliminating the disadvantages may cause the risk of demanding the fine setting including adjustment of full length of the short-sized golf club shaft.

The shaft gravity center of the generally employed short-sized shaft body (golf club shaft) is positioned closer to the proximal-end side than the position corresponding to 48% or 50% (in excess of the upper limit of condition formula significantly).

FIG. 5 represents properties of three samples of the golf club shaft 100 according to the embodiment. As FIG. 5 represents, samples 1, 2, 3 are prepared, each having its full length of 43 inches or longer in the initial state (for example, 45 inches or longer), and different properties. Each of the samples 1 to 3 has its shaft proximal-end side and shaft distal-end side partially cut so that the cut amount of the shaft at the proximal-end side is larger than that of the shaft at the distal-end side. Each position of the shaft gravity centers of the respective samples is monitored in each case of the shaft full lengths of 43 inches, 42 inches, 41 inches, and 40 inches, respectively.

In the case of the sample 1, when the shaft full length is 43 inches, the position of the shaft gravity center is set to 40.5%, when the shaft full length is 42 inches, the position is set to 40.2%, when the shaft full length is 41 inches, the position is set to 39.9%, and when the shaft full length is 40 inches, the position is set to 39.6%.

In the case of the sample 2, when the shaft full length is 43 inches, the position of the shaft gravity center is set to 42.6%, when the shaft full length is 42 inches, the position is set to 42.3%, when the shaft full length is 41 inches, the position is set to 42.0%, and when the shaft full length is 40 inches, the position is set to 41.7%.

In the case of the sample 3, when the shaft full length is 43 inches, the position of the shaft gravity center is set to 44.4%, when the shaft full length is 42 inches, the position is set to 44.1%, when the shaft full length is 41 inches, the position is set to 43.8%, and when the shaft full length is 40 inches, the position is set to 43.5%.

In the embodiment, the weight ratio of the metal cylinder 120 to the shaft body 110 of the golf club shaft 100 is set to be in the range from 14% to 33%. It is preferable to set the weight ratio of the metal cylinder 120 to the shaft body 110 to be in the range from 17% to 30%, and more preferably, from 20% to 25%.

By setting the weight ratio of the metal cylinder 120 to the shaft body 110 to be in the above-described range, various parameters of the golf club shaft 100 such as weight, frequency, and torque may be easily adjusted. Facilitating the gravity center shifting effect of the metal cylinder 120 allows easy setting of the shaft gravity center position to be in the range from 39% to 45%.

If the weight ratio of the metal cylinder 120 to the shaft body 110 is higher than 33% (in excess of the upper limit of condition formula), it is difficult to adjust various parameters of the golf club shaft 100 such as weight, frequency, and torque.

If the weight ratio of the metal cylinder 120 to the shaft body 110 is lower than 14% (below the lower limit of condition formula), it is difficult to obtain the gravity center shifting effect of the metal cylinder 120. For example, it is difficult to set the shaft gravity center to be positioned in the range from 39% to 45%.

In the case of the sample 1, when the shaft full length is 43 inches, the weight ratio of the metal cylinder 120 to the shaft body 110 is set to 29.8%, when the shaft full length is 42 inches, the weight ratio is set to 30.5%, when the shaft full length is 41 inches, the weight ratio is set to 31.4%, and when the shaft full length is 40 inches, the weight ratio is set to 32.2%.

In the case of the sample 2, when the shaft full length is 43 inches, the weight ratio of the metal cylinder 120 to the shaft body 110 is set to 22.1%, when the shaft full length is 42 inches, the weight ratio is set to 22.7%, when the shaft full length is 41 inches, the weight ratio is set to 23.3%, and when the shaft full length is 40 inches, the weight ratio is set to 24.0%.

In the case of the sample 3, when the shaft full length is 43 inches, the weight ratio of the metal cylinder 120 to the shaft body 110 is set to 18.1%, when the shaft full length is 42 inches, the weight ratio is set to 18.6%, when the shaft full length is 41 inches, the weight ratio is set to 19.2%, and when the shaft full length is 40 inches, the weight ratio is set to 19.8%.

FIG. 6 represents an example of change in the shaft outer diameter (O.D. (mm)) of the golf club shaft 100 in the longitudinal direction (X(mm)) according to the embodiment. The data of FIG. 6 have been acquired after cutting the shaft body to have its full length of 43 inches or shorter.

As FIG. 6 represents, the shaft body 110 includes a first region A1, a second region A2, and a third region A3 sequentially arranged from the proximal-end side toward the distal-end side in the longitudinal direction. In the first region A1, the shaft outer diameter of the shaft body 110 is relatively gently reduced from the proximal-end side toward the distal-end side in the longitudinal direction. In the second region A2, the shaft outer diameter of the shaft body 110 is relatively steeply reduced from the proximal-end side toward the distal-end side in the longitudinal direction. In the third region A3, the relative change amount of the shaft outer diameter of the shaft body 110 becomes the smallest in the longitudinal direction (substantially straight). The grip 300 is attached to the outer circumferential surface of the first region A1 of the shaft body 110. The metal cylinder 120 is buried in the inner circumferential surface of the third region A3 of the shaft body 110.

Preferably, each occupancy percentage of the first region A1, the second region A2, and the third region A3 in the longitudinal direction satisfies the following condition formulae. That is, preferably, the occupancy percentage of the first region A1 in the longitudinal direction is 30% or higher, the occupancy percentage of the second region A2 in the longitudinal direction is in the range from 45% to 60%, and the occupancy percentage of the third region A3 in the longitudinal direction is in the range from 10% to 25%. Referring to the example of FIG. 6, the occupancy percentage of the first region A1 in the longitudinal direction is set to 32%, the occupancy percentage of the second region A2 in the longitudinal direction is set to 50%, and the occupancy percentage of the third region A3 in the longitudinal direction is set to 18%.

By setting the occupancy percentage of the first region A1 in the longitudinal direction to 30% or higher, the first region A1 may be secured as an attachment region of the grip 300. When holding the grip 300 with both left and right hands, if the region to be held with the right hand is thinner than the region to be held with the left hand, the grip 300 is held with the right hand under the grasping power stronger than needed. This may raise the probability of making a miss shot.

By setting the occupancy percentage of the gently tapered first region A1 to 30% or higher to secure the attachment region of the grip 300, each thickness of the regions held with both left and right hands is made substantially the same. This may prevent the grip 300 to be held with the right hand from bearing the grasping power stronger than needed, raising the probability of making a nice shot.

On the contrary, if the occupancy percentage of the first region A1 in the longitudinal direction is set to be lower than 30%, the attachment region of the grip 300 extends across the first region A1 and the second region A2. This may make the region to be held with the right hand thinner than the region to be held with the left hand. The grip 300 to be held with the right hand bears the grasping power stronger than needed, resulting in raised probability of making the miss shot.

By setting the occupancy percentage of the third region A3 in the longitudinal direction to be in the range from 10% to 25%, the third region A3 may be secured as a burying region of the metal cylinder 120, and various parameters of the golf club shaft 100 such as weight, frequency, and torque may be easily adjusted.

As described above, the metal cylinder 120 is buried in the inner circumferential surface of the third region A3 of the shaft body 110. If the occupancy percentage of the third region A3 in the longitudinal direction is lower than 10%, it is difficult to secure the third region A3 as the burying region of the metal cylinder 120.

If the occupancy percentage of the third region A3 in the longitudinal direction is higher than 25%, it is difficult to adjust various parameters of the golf club shaft 100 such as weight, frequency, and torque.

By setting the occupancy percentage of the second region A2 in the longitudinal direction to be in the range from 45% to 60%, excellent sense (feeling) of strike motions may be obtained. This also makes it possible to secure the first region A1 as the attachment region of the grip 300, and the third region A3 as the burying region of the metal cylinder 120.

If the occupancy percentage of the second region A2 in the longitudinal direction is lower than 45%, the taper ratio (diameter reduction degree) of the golf club shaft 100 (shaft body 110) becomes too steep. This may cause the risk of making the sense (feeling) of strike motions unnatural.

If the occupancy percentage of the second region A2 in the longitudinal direction is higher than 60%, the first region A1 cannot be secured as the attachment region of the grip 300, and/or the third region A3 cannot be secured as the burying region of the metal cylinder 120.

FIG. 7 represents an example of change in each of the shaft outer diameters in the longitudinal direction of the golf club shaft 100 of the embodiment, and golf club shafts of comparative examples 1 to 3. The explanation on the change in the shaft outer diameter of the golf club shaft 100 of the embodiment has been made with reference to FIG. 6. By contrast, each of the golf club shafts of the comparative examples 1 to 3 is not divided into regions such as the first region A1, the second region A2, and the third region A3. Each of the regions has its diameter reduced from the proximal-end side toward the distal-end side with substantially the constant taper ratio across the entire region in the longitudinal direction.

A deformed mandrel (not illustrated) is prepared for manufacturing the above-described golf club shaft 100. An outer radial configuration of the mandrel includes a gently tapered surface (for example, taper ratio of 5/1000) for forming the first region A1, a steeply tapered surface (for example, taper ratio of 13/1000) for forming the second region A2, and a substantially straight surface for forming the third region A3. Then the inner circumferential surface of the metal cylinder 120 is fitted with the substantially straight surface of the deformed mandrel. Multiple prepregs are laminatingly wound on the outer circumferential surface of the deformed mandrel and the metal cylinder 120. The multiple prepregs are thermally cured to form the golf club shaft 100 having the shaft body 110 and the metal cylinder 120 integrated. Finally, the deformed mandrel is pulled out from the golf club shaft 100 for removal.

FIG. 8 represents an example of the laminated prepreg structure which forms the shaft body 110. The laminated prepreg structure is constituted by laminating carbon prepregs P1 to P8 in this order on the upper layer of the metal cylinder 120. Each of the carbon prepregs P1, P4 is a 0° prepreg having its long fiber direction parallel to the shaft longitudinal direction, and is disposed partially on the distal-end side in the longitudinal direction as a partial prepreg. Each of the paired carbon prepregs P2, P3 is a full-length bias prepreg having its long fiber direction at an angle of +/−45° to the shaft longitudinal direction, and extending across the entire longitudinal length. Each of the carbon prepregs P5 to P7 is a 0° prepreg having its long fiber direction parallel to the shaft longitudinal direction, and extending across the entire longitudinal length as a full-length prepreg. The carbon prepreg P8 is a 0° prepreg having its long fiber direction parallel to the shaft longitudinal direction, and wound on the deformed mandrel at the distal-end side, serving as a reinforced prepreg. The laminated prepreg structure as represented by FIG. 8 is one of exemplary cases. The number or each structure of the laminated prepregs may be variously modified.

Advanced golf players participated in the trial shot testing as testers requested to use the golf club shaft 10 of the embodiment, and a golf club shaft formed by attaching a heavier club head to the generally employed short-sized golf club shaft. Most of the testers felt that the sense (feeling) of strike motions when using the golf club shaft 10 of the embodiment was better than the use of the comparative one.

In the embodiment, the explanation has been made with respect to the use of the metal cylinder 120 buried in the inner circumferential surface of the shaft body 110 as the “gravity center shifting member, weight” for adjusting the position of the shaft gravity center. The “gravity center shifting member, weight” may be embodied into an arbitrary form with the degree of freedom as well as various modifications of design. For example, the metal containing prepreg may be contained in the prepregs constituting the shaft body 110 so that the resultant prepreg structure serves as the “gravity center shifting member, weight” for adjusting the position of the shaft gravity center. The laminated prepreg structure constituting the shaft 110 may be arbitrarily devised to serve as the “gravity center shifting member, weight” for adjusting the position of the shaft gravity center.

The golf club shaft and the golf club according to the embodiment, for example, for golf players, are suitable for offering excellent feel of swing motions without demanding the fine setting while keeping advantages of the short-sized golf club shaft.

While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A golf club shaft, comprising: a shaft body which extends in a longitudinal direction; and a gravity center shifting member which is attached to the shaft body for shifting a shaft gravity center toward a distal-end side in the longitudinal direction, wherein in the case of cutting the shaft body to have a shaft full length of 43 inches or shorter, and defining positions of a distal-end portion and a proximal-end portion in the longitudinal direction by percentage as 0% and 100%, respectively, a position of the shaft gravity center is set to be in a range from 39% to 45%.
 2. The golf club shaft according to claim 1, wherein a cut length of the shaft body at the proximal-end side in the longitudinal direction is longer than a cut length of the shaft body at the distal-end side in the longitudinal direction.
 3. The golf club shaft according to claim 1, wherein a weight ratio of the gravity center shifting member to the shaft body is set to be in a range from 14% to 33%.
 4. The golf club shaft according to claim 1, wherein the gravity center shifting member includes a metal cylinder buried in an inner circumferential surface of the shaft body.
 5. The golf club shaft according to claim 1, wherein the shaft body includes a first region having a shaft outer diameter relatively gently reduced, a second region having the shaft outer diameter relatively steeply reduced, and a third region having the smallest relative change amount of the shaft outer diameter, which are sequentially arranged from the proximal-end side toward the distal-end side in the longitudinal direction.
 6. The golf club shaft according to claim 5, wherein an occupancy percentage of the first region in the longitudinal direction is 30% or higher, an occupancy percentage of the second region in the longitudinal direction is in a range from 45% to 60%, and an occupancy percentage of the third region in the longitudinal direction is in a range from 10% to 25%.
 7. The golf club shaft according to claim 5, wherein a grip is attached to an outer circumferential surface of the first region, and a metal cylinder as the gravity center shifting member is buried in an inner circumferential surface of the third region.
 8. A golf club configured to have a club head and a grip attached to the golf club shaft according to claim
 1. 